Tramadol

Tramadol is a synthetic opioid-receptor agonist that has been used clinically as a narcotic analgesic since 1977. Tramadol also inhibits the reuptake of monoamines such as norepinephrine and serotonin, which enhances its analgesic effect. O-desmethyltramadol has 2-4 times the analgesic efficacy of the parent drug. In all body tissues and blood the drug concentration is greater than the N-desmethyl and O-desmethyltramadol metabolites, and O-desmethyltramadol is always greater in concentration than the N-desmethyl metabolite. There are numerous reports of tramadol toxicity and abuse. Overdoses of ≥500 mg may cause agitation, hypertension, tachycardia and seizures, while doses >800 mg may cause coma and respiratory depression.